Conservation of Bmp2 Post-transcriptional Regulatory Mechanisms

Abstract

Bone morphogenetic protein (BMP) orthologs from diverse species like flies and humans are functionally interchangeable and play key roles in fundamental processes such as dorso-ventral axis formation in metazoans. Because both transcriptional and post-transcriptional mechanisms play central roles in modulating developmental protein levels, we have analyzed the 3-untranslated region (3UTR) of the Bmp 2 gene. This 3UTR is unusually long and is alternatively polyadenylated. Mouse, human, and dog mRNAs are 83-87% identical within this region. A 265-nucleotide sequence, conserved between mammals, birds, frogs, and fish, is present in Bmp2 but not Bmp4. The ability of AmphiBMP2/4, a chordate ortholog to Bmp2 and Bmp4, to align with this sequence suggests that its function may have been lost in Bmp4. Activation of reporter genes by the conserved region acts by a post-transcriptional mechanism. Mouse, human, chick, and zebrafish Bmp2 synthetic RNAs decay rapidly in extracts from cells not expressing Bmp2. In contrast, these RNAs are relatively stable in extracts from Bmp2-expressing cells. Thus, Bmp2 RNA half-lives in vitro correlate with natural Bmp2 mRNA levels. The fact that non-murine RNAs interact appropriately with the mouse decay machinery suggests that the function of these cis-regulatory regions has been conserved for 450 million years since the fish and tetrapod lineages diverged. Overall, our results suggest that the Bmp2 3UTR contains essential regulatory elements that act post-transcriptionally.

Species-specific cis-Regulatory Elements in the 3′-Untranslated Region Direct Alternative Polyadenylation of Bone Morphogenetic Protein 2 mRNA

“…Consistent with its irreplaceable roles in development and postnatal physiology, BMP2 is evolutionarily conserved at the level of function as well as sequence (17,18). For example, the DPP (Drosophila decapentaplegic) protein, which is 71% identical to human BMP2, is functionally interchangeable with mammalian bone morphogenetic proteins in a mammalian bone induction assay (19).…”

“…Unusually well conserved sequences also occur in BMP2 noncoding regions. Indeed, the 3Ј-UTRs 3 of human and dog BMP2 transcripts include a region of 1080 nt that is 83% identical to the mouse transcript (18). The striking conservation of the 3Ј-UTRs of human, chimpanzee, several rodents, dog, deer, and cow implies vital post-transcriptional regulatory functions.…”

“…It has been suggested that the 3Ј-UTR is "a molecular hotspot for pathology" because of its major impact on tissue-specific gene regulation that, if disrupted, leads to developmental defects and lifethreatening diseases (27). Because alternative cleavage and polyadenylation is an important level of BMP2 gene regulation (18), we analyzed the mechanisms that control BMP2 poly(A) signal selection.…”

“…Alternative polyadenylation of the BMP2 3Ј-UTR yields two mRNAs differing only in their 3Ј-ends. Furthermore, the conserved region spanning the two poly(A) signals induces reporter gene expression in the mouse F9 embryonal carcinoma cell model of Bmp2 expression (18). Because poly(A) signal selection will include or exclude additional regulatory elements, such as micro-RNA and stability sequences, that may influence the function and metabolic fate of the mRNA, alternative polyadenylation may play a pivotal role in BMP2 expression.…”

“…Because poly(A) signal selection will include or exclude additional regulatory elements, such as micro-RNA and stability sequences, that may influence the function and metabolic fate of the mRNA, alternative polyadenylation may play a pivotal role in BMP2 expression. Interestingly, the relative abundance of long and short transcripts differed significantly in mouse and human cells and suggests that BMP2 poly(A) signal selection is species-or cell type-specific (18).…”